The invention relates to a water pump for a window washer unit of a vehicle, the pump having a reversible motor, one inlet port and two outlet ports and being arranged to deliver water selectively to either one of the two outlet ports in dependence upon the direction of rotation of the motor, wherein the pump comprises an impeller rotatable in a pump housing and a valve body surrounding the impeller and movable in dependence upon the direction of rotation of the motor to close the other of the two outlet ports.
Window washer unit for vehicles are already known from DE OS Nos. 23 34 390 and 24 34 492, which comprise separate spray nozzles for the windscreen and rear window and only one water pump which is reversible in its direction of rotation and has one inlet port and two outlet ports. The reversible water pump is connected in such a way that the two separate spray nozzle systems are selectively actuated in dependence upon the direction of rotation of the pump, non-return valves disposed in the hose pipes or arranged directly in the outlet ports ensuring that water is only sprayed from one of the two nozzles systems.
DE PS 30 23 897 discloses a further window washer unit of a vehicle, in which, instead of non-return valves being arranged at the outlet ports, a drive wheel is disposed concentrically with the impeller of the water pump and has a radially projecting extension which forms a flap valve serving to close the outlet ports alternately as a function of the direction of rotation of the water pump, the drive wheel being rotated by hydrodynamic forces.
This known device has the disadvantage that the drive wheel causes a deterioration in the efficiency of the pump since eddies arise on the driving webs provided on the drive wheel.
A water pump is known from DE OS 28 18 582, in which a valve body in the form of a drum disposed concentrically with the impeller of the water pump is driven by the drive shaft of the pump either directly or with the interposition of gearing, in order to leave one outlet port free intermittently.